Effective hemodialysis requires a blood flow of 250-300 ml/min. The usual method for obtaining this blood is placing two large needles into a fistula (arterialized vein) or a graft (PTFE conduit between artery and vein). Both needles are removed at the end of each treatment. The objective of this proposal is to further develop an Indwelling Fistula Assess Device (IFAD) which can be inserted into a fistula or graft, left in place for several weeks or months, and used for numerous hemodialysis treatments. Blood access would then be rapid, painless, and bloodless. The IFAD will be constructed from two sizes of stainless steel needle stock. A 20 gauge needle with point is welded into the front of a 17 gauge needle, near a sidehole in the larger needle (for blood removal or return). The small needle is inserted first into the fistula or graft, and rotation brings this needle through the skin, where a cap is placed to close it and to stabilize the device. The rotation also brings the side hole of the 17 gauge needle into the fistula. Animal tests with a similar 16 gauge device have shown that the IFAD can be left in place for up to 4 months, without clotting, phlebitis, or infection. This impressive biocompatibility is due to immobilization of the device, and to avoiding the trauma of a needle point within the fistula. During this project, in vitro tests will determine the hydraulic resistance of the IFAD. Animal tests will determine the longevity, biocompatibility, resistance to infection, and ease of removal of the device. If these tests are successful, an IDE proposal will be prepared for submission to FDA, for human testing of the device.